Best practice handling with big maps

Hi.

I have to build a new application to transform datas over mapping into another structure.

The map has round about 3500 fields. But each year the number of the fields can vary.

So I have to use the old map and the new map. That means each year I can have one more map.

The output should be handled by a web-Service.

My question is:

Is this something I should handle by ESB Toolkit (I haven’t used it so far) or the “normal” way using a flat file receive location and an Orchestration will do the mapping?

Thank in advanced for your ideas and help.

– Wolfgang